Phylogeographical structure within Boa constrictor imperator across the lowlands and mountains of Central America and Mexico

Aim: To evaluate the genetic diversity and phylogeographical structure of Boa constrictor imperator, in order to identify the key historical events responsible for its current distribution and diversity. Location: The Neotropical region of Mexico and mainland Central America. Methods: We used data from the mitochondrial cytochrome b gene, nuclear ornithine decarboxylase intron and microsatellites to perform spatial genetic analyses, and coalescence methods to infer phylogeographical structure, divergence times and historical demography. Results: Cytochrome b results revealed two main reciprocally monophyletic lineages, one along the Mexican Pacific coast and another along the Gulf of Mexico, Yucatán Peninsula and Central America, diverging c. 5.2 Ma. Both lineages are subdivided into haplogroups and show steady historical growth and a more recent population expansion. High genetic diversity was observed for both cytochrome b (h = 0.944) and microsatellites (HNei = 0.810-0.900). Main conclusions: We demonstrate deep phylogeographical structure with two reciprocally monophyletic lineages and five genetic clusters in Mexico and Central America. Our results suggest that several geographical barriers (including the Trans-Mexican Volcanic Belt and the Motagua-Polochic-Jocotán faults) and ecological features generated this structure. We report genetic diversity values for the boa at a regional scale and suggest that the two lineages may be considered distinct species.